Make and model of the unit is going to be needed. I know some work by simply grounding the wire.

Sold 6/30/06.
If you search, i posted how to do it three different ways...
The simple ground
With a switch
and with a relay
There are more complicated systems, and they need a hacked firmware upgrade to overide, but they are high end and/or factory models
edit
http://www.j-body.org/forums/read.php?f=4&i=127946&t=127736#127946
Read my post, about 9 posts down...
Edited 1 time(s). Last edited Tuesday, October 31, 2006 3:02 PM
for newer alpines, grab yourself a TR-7 module
-------------